Transgenic sterility in Populus: expression properties of the poplar PTLF, Agrobacterium NOS and two minimal 35S promoters in vegetative tissues

Transgenic sterility is a desirable trait for containment of many kinds of transgenes and exotic species. Genetically engineered floral sterility can be imparted by expression of a cytotoxin under the control of a predominantly floral-tissue-specific promoter. However, many otherwise desirable floral promoters impart substantial non-floral expression, which can impair plant health or make it impossible to regenerate transgenic plants. We are therefore developing a floral sterility system that is capable of attenuating undesired background vegetative expression. As a first step towards this goal, we compared the vegetative expression properties of the promoter of the poplar (Populus trichocarpa Torr. & Gray) homolog of the floral homeotic gene LEAFY (PTLF), which could be used to impart male and female flower sterility, to that of three candidate attenuator-gene promoters: the cauliflower mosaic virus (CaMV) 35S basal promoter, the CaMV 35S basal promoter fused to the TMV omega element and the nopaline synthase (NOS) promoter. The promoters were evaluated via promoter::GUS gene fusions in a transgenic poplar hybrid (Populus tremula L. x P. alba L.) by both histochemical and fluorometric GUS assays. In leaves, the NOS promoter conveyed the highest activity and had a mean expression level 5-fold higher than PTLF, whereas the CaMV 35S basal promoter fused to the omega element and the CaMV 35S basal promoter alone directed mean expression levels that were 0.5x and 0.35x that of PTLF, respectively. Differential expression in shoots, leaves, stems and roots was observed only for the NOS and PTLF promoters. Strongest expression was observed in roots for the NOS promoter, whereas the PTLF promoter directed highest expression in shoots. The NOS promoter appears best suited to counteract vegetative expression of a cytotoxin driven by the PTLF promoter where 1:1 toxin:attenuator expression is required.     

Selection for resistance, reversion towards susceptibility and synergism of chlorantraniliprole and spinetoram in obliquebanded leafroller, Choristoneura rosaceana (Lepidoptera: Tortricidae)

BACKGROUND: Obliquebanded leafroller, Choristoneura rosaceana (Harris), is an economic pest of pome fruits throughout North America. Repeated applications of broad‐spectrum insecticides have resulted in the development of resistance, cross‐resistance and multiple resistance in this pest. Studies were conducted to determine the possibility of resistance evolution, stability of resistance and the effect of metabolic synergists on toxicity of new reduced‐risk insecticides chlorantraniliprole and spinetoram in C. rosaceana. RESULTS: Larvae of C. rosaceana were selected for resistance to chlorantraniliprole and spinetoram in the laboratory. Significant levels of resistance to each insecticide were observed after 12 generations of selection. In the absence of selection pressure, susceptibility of a subset of larvae from both chlorantraniliprole‐ and spinetoram‐selected populations reverted to preselection levels after five and six generations respectively, indicating that resistance to both chlorantraniliprole and spinetoram was unstable in C. rosaceana. In synergist bioassays performed after 12 generations of selection, S,S,S‐tributylphosphoro trithioate (DEF) and piperonyl butoxide (PBO) synergized the toxicity of chlorantraniliprole and spinetoram respectively, suggesting the involvement of esterases in chlorantraniliprole resistance and the involvement of mixed‐function oxidases in spinetoram resistance. CONCLUSION: These findings suggest that chlorantraniliprole and spinetoram could be incorporated into C. rosaceana resistance management programs by using rotational strategies. Copyright © 2011 Society of Chemical Industry     

Somatic Embryogenesis in Maize and Comparison of Genetic Variability Induced by Gamma Radiation and Tissue Culture Techniques

Sixteen inbred lines and one hybrid of manse were tested for their capability of somatic embryogenesis, and fully developed plants could be regenerated, from ten inbred, lines. The highest frequency of plant regeneration was expressed in the inbred line CHI 31, and when this line was crossed with a recalcitrant, non-regenerating line, the F₁ and BC hybrids were regenerable. The results of reciprocal crosses demonstrated that dominant nuclear genes and cytoplasmic factors are primarily responsible for the heritable determination of embryogenic callus proliferation and in vitro regeneration of maize plants. Somaclonal and radiation-induced variability was studied in maize to assess their nature and potential contribution to plant breeding., The inbred line CHI 31 possessing a high in vitro capacity of somatic embryo formation was used as experiments.] material. CHI 31 plants were selfed and twelve-day old zygotic embryos irradiated with ⁶⁰Co gamma radiation in situ. Mature caryopses were harvested and assigned as M₁ material. In another series, immature zygotic embryos (size 1.2—1.5 mm) were cultured in vitro on N-6 medium supplemented with 2,4-D (2.5 μM), and somatic embryos regenerated into plants; these were transplanted into soil and self-pollinated. Regenerants from non-irradiated cultures were grown as R₁ generation, while regenerants from irradiated explants were considered as M₁R₁ generation. The genetic variability was evaluated in the M₂, R₂ and M₂R₂ generations, respectively, and compared with a non-treated seed control. Irradiation induced a variety of chlorophyll and morphological variants segregating in the M; generation; however, the frequency of deviant types obtained in the R: generation (somaclonal variation) was significantly exceeding the one derived from the M₂ populations. The combination of expert irradiation and in vitro regeneration was most effective for the manifestation of chlorophyll and morphological o if types in the M₂R₂ generation, and increased drastically the frequency of early flowering variants. Differences in the segregation patterns of mutant phenotypes amonsister somaclones in the R₃ and M₃R₃ generations indicate a different genetic basis, of plants originating from the same explant. This phenomenon suggests a mutational sectoring of the callus during culture. Radiation induced and somaclonal variation exerted a similar spectrum of chlorophyll and morphological deviants.     

The possible adaptive advantages of terrestrial egg deposition in some fluvial diadromous galaxiid fishes (Teleostei: Galaxiidae)

Several diadromous New Zealand and Australian species of Galaxias are now known, or suspected, to deposit their eggs amongst riparian vegetation or substrates either supratidally in estuaries or in forested streams in locations that are only temporarily submerged by elevated water levels. The eggs develop in a humid atmosphere and hatch when the egg deposition sites are resubmerged; a significant role for agitation in stimulating hatching seeming likely. There are risks from the eggs becoming dehydrated, and also from a failure by water to resubmerge the eggs before they have exhausted their energy resources. Hatching is triggered by elevated flows, perhaps being an outcome of agitation of the eggs. Elevated flows may also increase the rate of downstream transport of the larvae, facilitating survival during dispersal to sea from spawning sites in streams that may be long distances inland. Hatching during flood events may favour survival of the larvae because turbid flows may provide ‘cover’ for the larvae as they emigrate to sea. Risks from egg predation by aquatic predators may be replaced by risks from terrestrial predators.     

Genetic improvement of Trichoderma ability to induce systemic resistance

The beneficial applications of Trichoderma spp. in agriculture include not only the control of plant pathogens, but also the improvement of plant growth, micronutrient availability, and plant tolerance to abiotic stress. In addition, it has been suggested that these fungi are able to increase plant disease resistance by activating induced systemic resistance (ISR) . The mode of action of these beneficial fungi in the Trichoderma -plant-pathogen interaction are many, complex and not comple…     

Study of Sperm Concentration,Seminal Plasma Composition and their Physiological Correlation in the Persian Sturgeon,Acipenser persicus

The objectives of the present study were to determine ionic and organic composition of seminal plasma, sperm concentration and their relationships in the Persian sturgeon (Acipenser persicus). In this regard, ionic content (Na⁺, K⁺, Cl^?, Ca²⁺ and Mg²⁺) and organic content (total protein, glucose, cholesterol and triglyceride) along with sperm concentration were measured in 17 specimens of the Persian sturgeon. The seminal plasma contained 59.53 ± 2.56 mm /l sodium, 9.1 ± 1.42 mm chloride, 4.72 ± 0.3 mm potassium, 1.45 ± 0.075 mm calcium and 0.7 ± 0.072 mm magnesium. The following organic contents were found: total protein 0.11 ± 0.02 g/dl, glucose 22.18 ± 4.16 mg/dl, cholesterol 6.67 ± 1.04 mg/dl and triglyceride 15.2 ± 0.65 mg/dl. The mean sperm concentration was estimated to be 1.6 ± 0.12 (×10⁹ sperm/ml). A significant relationship was found between sperm concentration and K⁺ of seminal plasma (r = 0.533, p < 0.05). Significant correlations were observed between ionic contents: Na⁺ vs Cl^? (r = ?0.854, p < 0.01) and Mg²⁺ vs K⁺ (?0.583, p < 0.05). Also, level of triglyceride was negatively correlated with Mg²⁺ (r = ?0.503, p < 0.05). Presented data could be considered as a complementary study for developing special extenders and protectant solutions for improving artificial fertilization in this valuable species.